Polymer composition including polyacrylonitrile polymers and process for preparing same

ABSTRACT

There is disclosed a process for producing a novel polymer composition comprised of a polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences wherein the polymer composition is formed by the removal of a solvent from a solution of a polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences.

This is a division of application Ser. No. 166,032, filed July 7, 1980now U.S. Pat. No. 4,379,874.

FIELD OF INVENTION

This invention relates to novel polymer compositions includingpolyacrylonitrile polymers and more particularly to novel polymercompositions including polyacrylonitrile polymers and block copolymerswith an acrylonitrile sequence, and process for preparing same.

BACKGROUND OF THE INVENTION

Crystalline polyacrylonitrile polymers have been produced for many yearsand are basically utilized in the production of acrylic and modacrylictextile fibers. Polyacrylonitrile polymers have several distinguishingstructural features and physical properties including high degree ofcrystallinity with little amorphous phase; orientable at temperatures ofabout 100° C.; poor mechanical properties in an unoriented form andnon-melting. Notwithstanding low production costs and some desirableproperties, polyacrylonitrile polymers have only found limitedcommercial usages primarily including thin-walled articles prepareddirectly from solution and exhibiting enhanced mechanical propertiesafter orientation.

Block polymers of an acrylonitrile sequence with another polymersequence, for example, acrylamide are a two phase structure separatedinto domains wherein the acrylonitrile domain has like crystallinestructure to polyacrylonitrile polymer. Such a block copolymer may bereadily formed by the controlled acid hydrolysis of polyacrylonitrilepolymer and are highly available in water with a swelling capacitydependent on the ratio of both sequences and on the number of separatedomains. Generally, such a block copolymer exhibits considerablestrength in the swollen state caused by the two phase structure andcrystallinity of the acrylonitrile domains. Such block copolymers havebeen shaped by pressure in the swollen state or from thermo-reversiblegels (TRG), such as disclosed in U.S. Pat. Nos. 4,053,442 and 4,173,606,respectively.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a novel polymercomposition.

Another object of the present invention is to provide a novel polymercomposition comprised of a mixture of polyacrylonitrile polymers andblock copolymers of acrylonitrile with a non-crystalline polymersequence.

Still another object of the present invention is to provide a novelpolymer composition comprised of a mixture of polyacrylonitrile polymerand block copolymers of acrylonitrile with a non-crystalline polymersequence and exhibiting the more desirable properties of the respectivepolymers.

A still further object of the present invention is to provide a novelpolymer composition comprised of a mixture of polyacrylonitrile polymersand block copolymers of a arylonitrile polymers with a non-crystallinepolymer sequence and capable of forming bulky articles.

A further object of the present invention is to provide a novel polymercomposition comprised of a mixture of polyacrylonitrile polymers andblock copolymers of acrylonitrile with a non-crystalline polymersequence and capable of being stretched or oriented at roomtemperatures.

Still another object of the present invention is to provide a processfor preparing such a novel polymer composition.

A further object of the present invention is to provide a process forpreparing such a novel composition from polyacrylonitrile polymers andblock copolymers of acrylonitrile with a non-crystalline polymersequence.

A still further object of the present invention is to provide a processfor preparing such novel composition from polyacrylonitrile polymers andblock copolymers of acrylonitrile with a non-crystalline polymersequence in a form for facile subsequent processing.

SUMMARY

These and other objects of the present invention are achieved by formingin a solvent system a solution of polyacrylonitrile polymers and blockcopolymers of acrylonitrile with non-crystalline polymer sequence andsubsequently removing the solvent system to form a novel polymercomposition. In one aspect of the present invention, the properties ofthe novel polymer composition are preselectable by varying the molecularweight and/or weight percent of polyacrylonitrile polymer in thesolution and by varying the molecular weight and/or weight percent ofpolyacrylonitrile polymer in the solution and by varying the molecularweight, weight percent and/or lengths of the acrylonitrile andnon-crystalline polymer sequences of the block copolymers as well as bythe functional groups of the non-crystalline polymer sequence.

DETAILED DESCRIPTION OF PRESENT INVENTION

The polymer composition of the present invention is produced by formingin a solvent system a solution of polyacrylonitrile polymers and blockof copolymers of acrylonitrile with non-crystalline polymer sequence andsubsequently removing the solvent system. The term polyacrylonitrilepolymer, as used herein, is defined as polymers and copolymers ofacrylonitrile containing more than 85 molar percent of acrylonitrileunits being crystalline in the solid state and exhibiting a typicalX-ray diffraction pattern of of polyacrylonitrile (i.e. the mainreflexion corresponding to a periodicity of 5.1 Å and lateralorientation under stress).

The term block copolymers of acrylonitrile with a non-crystallinepolymer sequence is the block copolymer having an acrylonitrile sequenceand another polymer sequence, a two phase structure with anacrylonitrile domain and a polymer domain of polar groups wherein theacrylonitrile domain exhibits like crystalline structure topolyacrylonitrile and the polymer domain exhibiting an amphorusstructure. The acrylonitrile sequence is a continuous sequence ofacrylonitrile units of a mean molecular weight of at least about 500.The polar groups increase the moldulus of elasticity and slip limit ofthe polymer composition in the dry state. Additionally, the term blockcopolymer includes multiblock copolymers, i.e. two or more sequenceseach and generally preferably at least three sequences with the sequencefor the non-crystalline polymer sequence formed of at least about 10units. The amount of the acrylonitrile sequence of the block copolymeris from about 75 to about 1 weight percent, preferably of from about 50to about 5 weight percent based on the polymer composition.

For one set of polymer composition, the amount of polyacrylonitrilepolymer in such polymer composition is from 50 to 99 percent by weight,preferably 50 to 95 percent by weight of a molecular weight, of from30,000 to 1,500,000, preferably 50,000 to 1,000,000 with thenon-crystalline polymer sequence amounting to from 0.2 to 15 percent byweight, preferably 1.0 to 10 percent by weight of a molecular weight offrom 3,000 to 1,500,000, preferably 10,000 to about 500,000. For apolymer composition exhibiting physical properties of increased tensilestrength in both the dry and swelled state and of increased thermalstability in the swelled state, the amount of polyacrylonitrile polymersis from 0.5 to 40 weight percent, preferably 1.0 to 25.0 weight percentwith the non-crystalline polymer sequence amounting to 30 to 99 weightpercent, preferably 30 to 90 weight percent.

As hereinabove discussed, the amount of the block copolymer in thepolymer composition may vary between 0.2 to 99 percent with smallconcentrations improving the properties of the polymer composition sincethe non-crystalline polymer sequence functions as a surface-activeagent. The swellability of the polymer composition increases withincreasing concentrations of the non-crystalline polymer sequence andthus end usage of the polymer composition determines the amount ofnon-crystalline polymer sequence. It is noted that a polymer compositionhaving an amount of the non-crystalline polymer sequence in excess ofabout 20 weight percent is significantly swellable in solvents of thenon-crystalline polymer sequence.

The properties of the polymer composition are also dependent on themolecular weight of polyacrylonitrile polymer and the block copolymer.Generally, the component present in minor amounts in the finalcomposition can have a rather low molecular weight without loss of themechanical properties of the polymer composition. The molecular weightof the minor component should be at least about 3,000 and preferablymore than about 10,000, while the molecular weight of the majorcomponent should be at least about 30,000 and preferably at least50,000. The upper values of molecular weight are limited byprocessability of the composition. The molecular weight of the minorcomponent should not exceed about 1,000,000, with a preferably upperlimit of about 500,000. As a rule, the molecular weight of the majorcomponent as high as 1,500,000 are processable.

The processing properties of the solution also depend on the molecularweight of each polymer component as well as their weight ratios. Forease of processing, rather low molecular weights of both polymercomponents are preferred with a range of between 40,000 and 250,000usually satisfying demands of both processing and properties of thefinal product.

The properties of the polymer composition are also dependent on thenumber of acrylonitrile and non-crystalline polymer sequences per blockin copolymer. Increased number of sequences per block copolymer chainincreases the stability of the adsorption of the acrylonitrile sequenceon the polyacrylonitrile surface.

A preferred polymer composition is obtained when the non-crystallinepolymer sequence of the block copolymer is formed by units of highlypolar groups of a volume larger than the volume of a nitrile group. Suchunits include the acrylamide, N-substituted acrylamide, acrylic acid,salts of acrylic acid, esters of acrylic acid, hydrazides of acrylicacid, N-substituted hydrazides of acrylic acid and glutarimide. Anadvantage of such units is that they can formed by reactions of thecyano groups in the polyacrylonitrile polymer. Also advantageouslysignificant is the use of a block copolymer where the non-crystallinepolymer sequence are formed by two or more different groups, e.g.,copolymers of acrylamide with acrylic acid or with N-substitutedacrylamide or with an ester of acrylic acid, etc.

Generally, the solvent system includes at least a solvent forpolyacrylonitrile polymer, such as dimethylsulfoxide, dimethylformamide,demethyl acetamide, dimethyl methoxyacetamide, N-formyl morpholine,N-formylhexamethylene imine, cyclic hexamethylene sulfone,1,2,3-trithiocyano propane, gammathiocyanobutyronitrile; some cycliclactones and lactames; carboxylic acids, such as formic acid andhalogenacetic acids, nitric acid with a concentration higher than 50%,70 to 85% sulphuric acid, hydrofluoric acid, phosphoric acid, cyclicethylene carbonate, aqueous solutions of zinc chloride, lithium,potassium, sodium or calcium rhodanide, alkali metal perchlorates,lithium bromide, etc. Another suitable solvent systems are solutions ofthe above solvents with minor amounts of solvents capable of solvatingthe non-crystalline polymer sequence, e.g. water, glycols or glycerols,if the non-crystalline polymer sequence consists of the highly polargroups, such as acrylamide.

The range of concentration of the polymer components i.e.polyacrylonitrile polymer and block copolymer in the solution is fromabout 5 to about 80 percent by weight, advantageously from 15 to about70 percent by weight. At concentrations above about 35 percent byweight, the solution may be processed by heavy equipment such asextruders, calanders, kneaders, presses and the like because highlyconcentrated solutions behave more as a gel or a rubber than as asolution. Such highly concentrated solution yield very compact productswith small amounts of solvents to be recovered with processingadvantageously effected at elevated temperatures, which as a rule, islimited to the boiling point of the solvent.

At a concentration range of from about 15 to about 30 percent by weightof the solution, the polymer composition may be processed from thesolution or by the TRG method to produce membranes, tubings, fibers,layers on substrates, etc.

A polymer composition with high concentration of the non-crystallinepolymer sequence is thus substantially swellable with solvents therefor,and can be advantageously processed by these methods since swelling ofthe final article diminishes the contraction caused by thesolution-solid transition. The TRG method for processing a polymercomposition differs from the same method used for processing thepolyacrylonitrile of the multiblock copolymers, Since higherconcentration of the polymer components can be used yielding stronger,tougher and more stable products.

Formation of the polymer solution of the polymer components in a solventsystem may be effected in a plurality of methods. In one method, thepolymer components are dissolved in the common solvent using stirring,kneading and homogenization equipment. The concentration of the polymercomponents in the mixture is limited by the viscosity which allowshomogenization. Such method is preferred for the preparation of lowconcentrate solutions, and permits the use of heavy homogenizationequipment to prepare solutions containing as much as 50 percent byweight of the polymer components. Additionally the use of inertsolvents, in such a solution permits operation at elevated temperaturesthereby facilitating homogenization.

Another method involves the polymerization of acrylonitrile in a blockcopolymer solution and is advantageous in the preparation of veryviscous mixtures without resort to homogenization equipment. Onepreferred solvent for such method is a zinc chloride solution permittingof the preparation of the mixture without isolating any intermediateproduct. This method is suitable for the preparation of a product of thepolymer composition with fibers and fillers, since the fibers and/orfillers may be added to the solution before completion of thepolymerization of the acrylonitrile, i.e. at low viscosities of thesolution.

Still another method comprises the formation of the block copolymer in apolyacrylonitrile solution, preferably preparing the block copolymer ofacrylonitrile with the non-crystalline polymer sequence from thepolyacrylonitrile units, e.g. by the hydrolysis of polyacrylonitrilepolymer in the presence of 50 to 72 weight percent nitric acid to yielda multiblock copolymer having acrylonitrile and acrylamide sequences.The hydrolysis of polyacrylonitrile polymer is an accelerating reactionwith the rate strongly decreasing with increasing concentration of thepolyacrylonitrile polymer in solution. It is also known that themonomeric acrylonitrile acts as a precititant for polyacrylonitrilepolymer.

It has been found that the polymerization of acrylonitrile in nitricacid is accompanied by the precipitation of solid polyacrylonitrilepolymer, if the initial concentration of acrylonitrile is sufficientlyhigh and/or the temperature is sufficiently low. As the polymerizationproceeds and the concentration of acrylonitrile decreases, theprecipitated polyacrylonitrile polymer slowly dissolves into solutionand the dissolved portion initiates hydrolysis at a low concentration ofpolyacrylonitrile polymer in solution while the remaining precipatedportion is protected against hydrolysis. The dissolved portion of thepolyacrylonitrile polymer has a considerable start before hydrolysis ofthe precipatated portion thereof which time difference leads to aconsiderable difference in the hydrolysis conversion whereby multiblockcopolymers are always simultaneously present in the mixture with intactpolyacrylonitrile chains. The resulting distribution of the hydrolysisconversion per polyacrylonitrile polymer chain is considerably broadenedwith a result similar to a mixture prepared by dissolvingpolyacrylonitrile polymer and the respective block copolymers. Moreover,there are considerable local fluctuations in the hydrolysis conversion,i.e. the chains are concentrated in some locations and the intactpolyacrylonitrile chains in other locations and improves the conditionsof the separation of the phases.

This last method of solution formulation is technologically advantageoussince concentrated solutions may be prepared in one step.

After formulation of the solution of the polyacrylonitrile polymer andthe block copolymer, removal of the solvent system is effected to formthe polymer composition as a result of polymer phase separation. Theconditions of solvent removal directly influence the size of thecrystalline domains and thus the properties of the resulting polymercomposition.

The higher the viscosity of the solution at the moment of the polymerphase separation, the larger is the number of crystalline domains, andtherefore, the larger is the apparent crosslinking density of the finalpolymer composition. Consequently, the modulus of elasticity increasesas the swelling capacity decreases with increasing concentration of thepolymer components in the solution at the moment of polymer phaseseparation.

Essentially, there are two methods of solvent removal, i.e. evaporationand extraction. The evaporation method dictates the need of a solventsystem of required volatility (e.g. dimethysulfoxide), and yields apolymer composition of high apparent crosslinking density since polymerphase separation is effected by high concentrations of the polymercomponents, i.e. at high viscosities. Evaporation techniques produce apolymer composition which may be shaped into membranes, fibers, layerson textile substrates, etc.

Extracting techniques utilize a suitable solvent to extract the solventsystem to coagulate the polymer composition. The extraction solvent isat least miscible with the polyacrylonitrile polymer solvent of thesolvent system, let alone totally miscible with the solvent system, perse. Preferably such an extraction solvent is water or dilute aqueoussolutions of the polyacrylonitrile solvents, such as the lower aliphaticalcohols (methanol, ethanol, isopropaniol and the like), glycerol,glycols and mixtures thereof. The extraction solvent should be misciblewith polyacrylonitrile polymer solvents while simultaneously capable ofprecipitating polyacrylonitrile polymer.

As hereinabove mentioned, the properties of the polymer compositiondepend upon the viscosity of the solution at the moment of separation ofthe polymer phases. The viscosity of the solution may be selected withinbroad limits depending mainly upon the concentration of each polymercomponents in the solution. Highly swellable (that is, physicallysparingly crosslinked) polymer compositions are preferably produced bycoagulating diluted solutions (e.g. 10-25 percent by weight of thepolymer components) whereas the non-swellable or slightly swellablepolymer compositions are prepared by the coagulation or precipitation ofhighly concentrated, gelatinous or rubberlike solutions or mixtures.

The methods of solvent removal may be combined. If the mixture containsboth a solvent and an extraction solvent, the resulting mixture forms aphysical gel at a certain temperature and a solution above suchtemperature. Mixing a more volatile solvent, such as dimethylsulfoxide,with a less volatile extraction solvent, such as glycerol andevaporating a portion of the solvent above the gelling temperature, aseparation of the polymer phases begins by cooling the solution to yielda tough gel which can be easily processed. The remaining portion ofsolvent and the extraction solvent may be separated by a more volatileliquid, such as water or methanol.

While the mechanism of formation of the polymer composition is not fullyunderstood, it is believed that the crystalline domains of theacrylonitrile sequence of the block copolymer orient themselves with thepolyacrylonitrile polymers with the non-crystalline polymer sequencecongregating with themselves thereby forming ordered regions ofcrystalline domains or phases embedded in amorphous matrix or viceversa, i.e. amorphous domains or phases embedded in a crystallinematrix.

It will be appreciated that the solution may be shaped before polymerphase separation. Dilute, low-viscosity solutions may be shaped byextrusion through a nozzle into a coagulation bath or by spreading ontoa textile support or substrate, etc. Any shaping technology is availablefor processing the polymer component solutions.

Highly concentrated solutions, which are more or less tough physicalgels, may be shaped by methods used for soft plastic or polymer melts,e.g. pressing, punching, extrusion, calendaring, injection-molding, etc.Shaping is followed by evaporation or extraction of the solvents system.Shaping may also be effected during coagulation and/or during subsequentwashing of the solvent residues in which case, shaping is accompanied byorientation.

The polymer composition may be shaped after all the polyacrylonitrilepolymer solvents are removed, preferably by applying pressure at atemperature above 75° C. and advantageously above 120° C. Such shapingis accompanied by orientation of the crystalline domains of the polymercomposition and thereby improving its mechanical properties. Shaping maybe effected while the polymer composition contains some extractionsolvent such as water or glycerol.

Water can be present in two forms, i.e. as true swelling water if thepolymer composition is water-swellable, or as so called "aquagel water",if the polymer composition is essentially not water-swellable. Sinceaquagel water is not equilibrial, a polymer composition cannot againswell once such polymer composition is dried.

The aquagel water content in a polymer composition is about 50 percentby weight, and similar to polyacrylonitrile polymer coagulates undersimilar conditions.

The aquagel water in a polymer composition in an "aquagelous state" canreadily be replaced by glycerol or the like. A polymer composition in anglycogelous state is more stable than a polymer composition in theaquagelous state. It has been found that the polymer composition ofeither an aquagelous or glycogelous states are very suitable for shapingat room temperature or at slightly elevated temperatures. The polymercomposition even if completely dry can be shaped at temperatures between10° to 210° C., preferably between 110° and 180° C. Shaping of thepolymer composition in a dry state is especially useful for finalshaping and orientation of an article of the polymer composition.

Polymer composition may be produced exhibiting many desirable physicalproperties depending on intended end use. For example, water-swellablepolymer compositions may be utilized as very strong hydrogels forprosthetic medicine in the production of permeable membranes,hydrophilic fibers, etc.

Non water-swellable polymer compositions may be utilized as areplacement for plastic or metallic structural components where physicalproperties, such as low weight, high strength, high impact resistance,low flammability, corrosion resistance, etc. are important designconsiderations. Thus, such polymer compositions can be used as tubes,containers or the like in contact with hydrocarbons, such as gasolene,since such polymer compositions are completely impermeable for non-polarcompounds. The polymer compositions may be combined withelectroconductive compounds to eliminate static charges. The property oflow heat conductivity renders the polymer compositions a compatibleouter laminate sheets with a foamed inner layer.

The water-swellable and non water-swellable polymer compositions may bereadily combined to form laminates of mechanically strong layers withintermediate hydrogel layers. It is known that hydrogel-coated surfacesexhibit lower hydrodynamic resistance then untreated hydrophobicsurfaces. Such decrease in hydrodynamic resistance is advantageouslyutilized either for transport of water, or for transport of a solid bodythrough water. Therefore, hydrogel layers on ships, inner surfaces ofpipes, centrifugal pumps, propeller blades and the like would increasethe efficiency of the respective device. Non water-swellable polymercompositions can be readily provided with a hydrogel layer, either fromthe hydrogel-like species of the polymer compositions or from thehydrogelous block copolymer to achieve a strong and desirable connectionwith a hydrogel and a hydrophobic solid surface, e.g. a metal, a plasticor a hydrophobic plastic.

Such a connection may be effected in any one of a plurality of methods.Thus, by one method, an article formed of the polymer composition iscovered with a solution of a block copolymer of acrylonitrile of anappropriate viscosity in a solvent system. Removal of the solvent systemcauses an integral hydrogel layer to be formed on the article. Anothermethod includes the steps of overlaying such a preformed article with apolymer components solution with subsequent solvent removal. Stillanother method includes the casting of a two polymer component solutionfollowed by solvent removal using extraction techniques to formconnected layers of different properties. A further method would includecontact between a preformed article of non water-swellable polymercomposition and a solution including a swelling and a hydrolyzing agentto form in situ a superficial layer of a hydrogel.

EXAMPLES OF THE INVENTION

The following examples are illustrative of conditions for the process ofthe present invention and it is to be understood that the scope of theinvention is not to be limited thereby.

EXAMPLE I

Fifteen (15) parts by weight of polyacrylonitrile polymer(M.W.--175,000) are dissolved in 85 parts by weight of 65% nitric acidand the solution maintained at 10° C. until about 75 molar % of thecyano groups are hydrolyzed. To the solution cooled to -5° C., there isadded 3.75 parts by weight of polyacrylonitrile polymer (M.W.--25,000).The solution is stirred to dissolve the polyacrylonitrile polymer withthe resulting solution being extruded through an annular orifice into awater coagulation bath. The thus formed hydrogel membrane exhibitedimproved properties of increased tensile strength and reduced increaseof the swelling capacity with increasing temperature, as compared to ahydrogel prepared without the subsequent introduction of anon-hydrolyzed polyacrylonitrile polymer.

EXAMPLE II

Ten (10) parts by weight of polyacrylonitrile polymer (M.W.--350,000)are dissolved in 70 parts by weight of aqueous 60 percent by weightsolution of NaSCN to which is added 5 parts by weight of NaOH dissolvedin 15 parts by weight of 60 percent by weight of NaSCN solution. Theresulting solution is heated to 75° C. for several hours and thehydrolyzed polyacrylonitrile coagulated with water and acidified withdiluted acetic acid. The resulting block copolymer containing about 45molar % of cyano groups and both carboxilic and amidic groups, is driedand milled to a powder. Fortyfive (45) parts by weight of powderedpolyacrylonitrile polymer, 5 parts by weight of the powdered blockcopolymer and 30 parts by weight of a very finely crystalline NaSCN arethoroughly mixed and evenly spread on a glass dish for subsequent steamexposure. The mixture gelatinated yielding a homogeneous rubber-likemixture which is then extruded into a 10 percent by weight solution ofNaSCN, washed with water and pressed into the shape of a sheet.

EXAMPLE III

Twenty (20) parts by weight of polyacrylonitrile polymer (M.W.--550,000)are dispersed into a mixture of twenty (20) parts by weight of dimethylsulfoxide (DMSO) and 80 parts by weight of isopropanol. One (1) part byweight of a diblock copolymer containing 70% mol. of AN and 30% mol. ofstyrene is added, with the dispersion being spread onto a tray havingcrimped polyester fibers arranged in a criss-cross fashion. Alcohol isevaporated into an oven, so that the residual DMSO dissolved thepolymers components forming a reinforced rubber-like sheet. The sheet isstretched onto a positive mold and put into the oven until the DMSO isevaporated to produce a pre-formed sheet which is pressed andsimultaneously oriented at 175° C.

EXAMPLE IV

The rubber-like sheet prepared in accordance with Example III is cutinto strips and introduced into a screw extruder together with finelypowdered ammonium carbonate. The barrel of the extruder is heated to 70°C. with its annular head heated to 150° C. An extruded foamed tube iswithdrawn from the head and washed with hot water. The wet tube isfilled with a solution of 7.5 percent by weight of NaOH and 42.5 percentby weight of NaSCN in water at 50° C. until a hydrogel layer is formed.The tube is then washed with water and dried. The resulting porous tubehaving an inner hydrogel lining exhibited excellent thermal-insulatingcapability and reduced hydrostatic resistance to water.

EXAMPLE V

An amount of 0.1 parts by weight of ammonium persulphate is dissolved in50 parts by weight of 65% nitric acid, and 50 parts by weight ofdistilled acrylonitrile added to the solution. The solution is thenpoured into a polypropylene mold filled with a mat of 2.5 cm. longcrimped polyacrylonitrile fibers (Orlon). The mold is placed into awater bath maintained at a temperature of 50° C. and is stored thereinfor 55 hours. The mold is thereafter opened and a sheet of rubber-like,turbid, reinforced composition is washed with water. A 10 mm. thicktough, china-like sheet is then rolled between crossed rollers heated to110° C. to form a pre-formed sheet having a thickness of 3 mm. The sheetis pressed into a mold to form one half of a rectangular vessel of afinal wall thickness of 1 mm. A vessel made of two such parts is testedas a gas tank.

EXAMPLE VI

The polymer composition prepared in accordance with Example I is dried,milled and dissolved in DMSO to yield a 20 percent by weight solution.The solution is heated to 120° C. with a 10 percent by weight ofglycerol thereafter added. The resulting solution is poured onto apreformed sheet of the polymer composition prepared in accordance withExample V and slowly cooled to effect gelatination. The resultinglaminate is washed with water, soaked with 10% aqueous glycerol anddried. The thus formed two layer laminate is shaped in a press toprovide a panel for ship hull construction. The thickness of thelaminate is about 6 mm. when the hydrogel is swelled with water.

While the invention has been described in connection with severalexemplary embodiments thereof, it will be understood that manymodifications will be apparent to those of ordinary skill in the art;and that this application is intended to cover any adaptations orvariations thereof. Therefore, it is manifestly intended that thisinvention be only limited by the claims and the equivalents thereof.

What is claimed:
 1. A process for producing a polymer composition whichcomprises:(a) forming a solution of polyacrylonitrile polymer and ablock copolymer with acrylonitrile and non-crystalline polymer sequenceswith an average number of said sequences per multiblock copolymer beingequal and at least 2 in a solvent system said acrylonitrile sequencehaving a mean molecular weight of at least 500, said non-crystallinepolymer sequence being comprised of at least about 10 units andconstituting one or more highly polar units selected from the groupconsisting of acrylamide, N-substituted acrylamide, acrylic acid, estersof acrylic acid, salts of acrylic acid, hydrazides of acrylic acid andglutarimide; and (b) separating said solvent system from said solutionto form a polymer composition.
 2. The process as defined by claim 1wherein said polyacrylonitrile polymer and said block copolymer areintroduced into said solvent system in an amount to form a solution ofless than 50 percent by weight of the solution.
 3. The process asdefined in claim 2 wherein said solution is formed by homogenizationtechniques.
 4. The process as defined in claim 1 whereinpolyacrylonitrile is formed by the polymerization of acrylonitrile in ablock copolymer solution.
 5. The process as defined in claim 4 whereinsaid solvent system includes a zinc chloride solution.
 6. The process asdefined in claim 5 wherein a material selected from the group consistingof fibers and fillers is added prior to step (b).
 7. The process asdefined in claim 1 wherein said block copolymer is formed by reacting insitu polyacrylonitrile under conditions to form non-crystalline polymersequences.
 8. The process as defined in claim 7 wherein saidpolyacrylonitrile is hydrolyzed in the presence of 50 to 72 weightpercent nitric acid.
 9. The process as defined in claim 1 wherein step(b) is effected by evaporation of the solvent.
 10. The process asdefined in claim 1 wherein step (b) is effected by extraction of thesolvent.
 11. The process as defined in claim 1 wherein saidpolyacrylonitrile polymer is added in an amount to form of from 50 to 99percent by weight of said polymer composition and said polyacrylonitrilehas a molecular weight of from 30,000 to 1,500,000.
 12. The process asdefined in claim 11 wherein said block copolymer is added in an amountso that the non-crystalline polymer sequence comprises of from 0.2 to 15percent by weight of said polymer composition.
 13. The process asdefined in claim 1 wherein said polyacrylonitrile polymer is added in anamount to comprise of from 0.5 to 40 percent by weight of said polymercomposition.
 14. The process as defined in claim 13 wherein said blockcopolymer is added in an amount so that the non-crystalline polymersequence comprises of from 30 to 99 percent by weight of said polymercomposition.